Prokaryotic Diversity: The Bacteria

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Chapter 12

• Prokaryotic Diversity The Bacteria

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12.7 Pseudomonas and Pseudomonads

• Straight or slightly curved gnb
• Chemoorganotrophs
• Aerobic rods with polar flagella
• Mesophiles

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Key Characteristics of Pseudomonads

• Absence of gas formation from glucose
• Positive oxidase test separate from enteric
  bacteria
• Many can use numerous organic compounds as C and
  energy sources
• Rarely have hydrolytic enzymes to break down
  polymers
• Usually found in the soil and water, can
  breakdown pesticides and other toxic substances
  possible agents of bioremediation

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Entner-Doudoroff Pathway

• Pseudomonads metabolize glucose with the
  Entner-Doudoroff pathway
• 2 key enzymes
• 6-phosphogluconate dehydrase
• 2-keto-3-deoxyglucosephosphate aldolase
• Pretty unique to the pseudomonads and several
  other groups

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Pathogenic Pseudomonads

• Pseudomonas aeruginosa
• urinary and respiratory tract infections
• common in severe burns or other traumatic skin
  damage
• Cystic fibrosis patients
• may become systemic
• usually resistant to most antibiotics due to the
  R factor (resistance transfer plasmid)
• responsible for nosocomial infections in hospitals

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12.10 Neisseria, Chromobacterium and Relatives

• Related by gram stain, morphology, lack of
  motility and aerobic metabolism
• Neisseria is a cocci
• Moraxella, Branhamella, Kingella and
  Acinetobacter are rod shaped that become coccoid
  in stationary phase
• Group is usually called coccobacillus

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Organisms Location

• Neisseria, Moraxella, Kingella isolate from
  animals
• Neisseria is the causative agent of gonorrhea
• Acinetobacter common soil/H2O organism,
  occasional nosocomial infections
• Acinetobacter and Moraxella twitching motility
  have special pili

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Chromobacterium

• Close relative but rod-shaped
• C. violaceum and few others create purple
  pigment violacein which has antibiotic-like
  properties
• produced only on medium that contains Trp
• Facultative anaerobe, fermentative on sugars,
  aerobically on variety of C source

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12.11 Enteric Bacteria

• Escherichia, Salmonella, Proteus and Enterobacter
• Gnb, non-sporulating, non-motile or motile by
  peritrichous flagella, facultative aerobes
• Oxidase negative, ferment sugars to a variety of
  end points
• Many are pathogenic to animals, humans and plants
• Very similar genome but keep separate for
  clinical reasons ID so can treat rapidly

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Fermentation Patterns

• Fermentation products from anaerobic fermentation
  of glucose
• mixed-acid fermentation 3 acids, lactic, acetic
  and succunic
• also make CO2, EtOH, H2 but not butanediol
  (purple broth)
• 2,3-butanediol fermentation
• small amount of acid form but butanediol (VP
  test)
• EtOH, CO2 and H2 are the main products, more than
  in mixed acid

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Butanediol Pathway

• Makes 2 extra CO2 per glucose molecule than seen
  in mixed-acid fermentation

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• This table and the previous one separate the
  mixed-acid producers from the butanediol ones
• These are approximations some strains may be
  negative for a commonly positive test

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Quick Identification Pathway
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Escherichia

• Intestinal tract synthesizes vitamins like K
• Use O2 in large intestine anoxic
• Use a wide range of C and energy sources
  sugars, AA, organic acids, etc
• Pathogenic strains cause diarrhea in infants in
  pediatric and OB wards and UTI in older patients
• E. coli strain implicated in dysentery-like
  infection with fevers
• makes K antigens that allow for attachment and
  colonization of small intestine
• enterotoxin is responsible for the symptoms of
  diarrhea

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Salmonella

• Closely related to E. coli
• Pathogenic to humans and other warm blooded
  animals
• cause typhoid fever and gastroenteritis
• 3 surface antigens that play role in infections,
  especially typhoid fever
• O or somatic Ag part of the lipopolysaccharide
  layer
• H or flagellar Ag
• Vi or outer polysaccharide Ag
• Use Ag o track strain in case of epidemic
  outbreak, not related to symptoms
• Lactose non-fermentor, H2S producer, grows in
  selenite broth

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Shigella

• Related to E coli
• Pathogenic to humans
• Severe gastroenteritis, bacillary dysentery
• Food/H2O bourne routes of infection
• Makes a endotoxin and neurotoxin that cause the
  enterotoxic effects
• Lactose non-fermentor, no lysine decarboxylase
  activity

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Proteus

• Rapid motility, produce urease
• Distant relationship to E coli
• Causes UTI
• Exhibit swarming because of motility, cells at
  edge are mote motile and spread out, settle down,
  become stationary, divide to make a new wave of
  movement

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Butanediol Fermentors

• Eneterobacter, Klebsiella and Serratia
• All are closely related

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Butanediol Fermentors

• Enterobacter aerogenes H2O/sewage as well as
  intestinal tract of warm blooded animals,
  occasional UTI pathogen
• Klebsiella pneumonia infect some humans causing
  pneumonia but usually found in soil/H2O, can fix
  N2
• Serratia forms red pyrrole-containing pigments
  prodigiosins, produced during stationary phase
  H2O/soil, gut of some insects, vertebrates and
  intestines of some humans

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12.12 Vibrio

• Gram negative, facultatively aerobic rods or
  curved rods
• Fermentative metabolism, polarly flagellated,
  oxidase positive
• confused with Pseudomonas which is
  non-fermentative
• Vibrio cholerae cause cholera in humans,
  doesnt infect other hosts, most common
  infectious disease in underdeveloped countries,
  transmitted almost exclusively by H2O

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12.13 Rickettsias

• Small, gram negative coccoid ir rod-shaped
  bacteria, all but 1 are obligate intracellular
  parasites
• Cant culture without host cells positive
• Cause typhus fever, Rocky Mountain spotted fever,
  Q fever
• Host cell and bacteria must be alive, replicate
  in cell and eventually rupture to release new
  bacteria

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12.14 Spirilla

• Gram negative, motile, spiral shape
• IDed by flagella pattern and O2 requirement,
  relationship to plants/animals, fermentive
  ability, and other characteristics
• Campylobacter and Helicobacter pathogens to
  human and other animals
• microphilic and isolated from clinical specimens
  incubated at low O2 (3-15) and high CO2 (3-10)
• Campylobacter acute enteritis, usually bloody
  diarrhea, have enterotoxin
• Helicobacter pylori related to Campy
  acute/chronic gastritis, lead to peptic ulcers

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12.19 Non-Sporulating Gram Positive Bacteria
Lactic Acid Bacteria and Relatives

• Staphylococcus, Micrococcus (really a
  Actinobacteria, similar to Staph so studied
  here), Streptococcus, Lactobacillus and Sarcina

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Staphylcoccus and Micrococcus

• See Table 24.3
• Both are aerobic, gram positive cocci, catalase
  positive, resistant to decrease H2O and tolerate
  drying and high salt fairly well (MSA), many
  species are pigmented
• Separate using oxidation/fermentation (O/F
  medium)
• Staph facultative aerobe, produce acid from
  glucose both aerobically and anaerobically, forms
  cell clusters
• Micro obligate aerobe, produce acid only
  aerobically, isolate from skin but more common on
  inanimate objects, dust and soil

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Staphylococcus

• Common commensal and parasites of humans/animals
  and occasionally cause serious infection
• 2 major species
• S. aureus yellow pigment, associated with
  pathological conditions boils, pimples,
  pneumonia, osteomyelitis, meningitis and
  arthritis
• S. epidermidis non-pigmented, non-pathogenic on
  skin and mucus membranes

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Lactic Acid Bacteria and Fermentors

• Gram positive coccus or bacillus that make lactic
  acid as major or sole fermentation product
• Obtain energy only by substrate level
  phosphorylation
• Grow anaerobically not sensitive to O2 can grow
  in its presence or absence aerotolerant
  anaerobes
• Restricted to growth in areas where sugars are
  present, usually limited biosynthetic activity,
  need much in terms of nutrients in enviroment

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2 Groups

• Homofermentative produce single sugar product
  lactic acid
• Heterofermentative produce other products as
  well as EtOH and CO2

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Heterofermentors

• Have no aldolase so cannot break down fructose
  bisphosphate to triose phosphate, rather oxidize
  glucose-6-PO4 to 6-phospho-glucinate,
  decarboxylate to pentose-PO4 (makes CO2) then to
  triose-PO4 and acetyl-PO4 by phosphoketolase
• Triose-PO4 converted to lactic acid
• Acetyl-PO4 picks up electron EtOH and only 1
  mol of ATP

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Homofermentors

• Have aldolase defining between homo- and
  hetero-fermentors
• Make lactic acid and 2 mol ATP

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Streptococcus and Other Cocci

• Variety of homofermentative species
• Some are pathogenic to humans and animals
• Play role in making buttermilk, silage and other
  fermented products and dental caries

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• Lactococcus streptococcus of dairy significance
• Eneterococcus streptococcus of fecal origin
• Streptococcus 2 groups based on hemolysis on BAP

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Streptococcus

• 2 groups 1) produce streptolysin O or S
  complete red blood cell lysis - ?-hemolysis and
  2) do not lyse cells but make brownish green zone
  on BAP, ? hemolysis (use only K)

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Immunological Groups of Strep

• Streptococcus also divided into immunological
  groups because of carbohydrates on the surface
  Lancefield groups
• A ag - ? hemolytic streps in humans
• D ag enterococcus
• B ag usually found in association with animals
• mastitis inflammation of the udder and certain
  human diseases

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Leuconostoc

• Heterofermentors used in dairy fermentation
• make dextran polysaccharides, used as a plasma
  extender, when grown on sucrose medium

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Lactobacillus

• Rod shaped, long and slender to short and bent
• Most are homofermenters with occasional
  heterofermenters
• L. delbrueckii used to make yogurt
• L. acidophilus used to make acidophilus milk
• Other members used to make silage, sauerkraut and
  pickels
• Usually resistant to acidic environments grow
  on tomato juice peptone agar
• Rarely, if ever, pathogenic

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Listeria

• Gram positive coccobacillus 3-5 cells
• Phylogenetically related to lactobacillus
• Produce acid but no gas from glucose
• Requires micro or fully oxic growth conditions
• Catalase positive (oxic and catalase are unique
  to Listeria)
• L. monocytogenes major food-bourne illness
  listeriosis
• usually caused by contaminated ready-to-eat food
  mainly cheese
• mild illness to fatal form of meningitis

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12.20 Endospore-Forming Gram Positive Bacteria

• Bacillus, Clostridium and relatives
• Cell morphology, shape and cellular position of
  endospore, relationship to O2 and energy
  metabolism

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Spore Formers

• 2 most common
• Bacillus aerobic and facultative aerobes
• Clostridium strictly anaerobic, fermentative
  species
• Endospore forming are ecologically related
  because in nature are found in soil even those
  which are pathogenic to humans
• infect hosts only incidentally
• production of endospores is an advantage as soil
  is highly variable in nutrients, temperature and
  H2O amounts can remain dormant for long periods
• Can kill vegetative cells by heating to 80 for
  10 minutes, place endospores on media and get
  bacillus or clostridium (dependent on O2)

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Bacillus and Paenibacillus

• Temperature and endospore location are on the
  next table
• Grow on defined media with a number of C sources,
  produce hydrolytic enzymes that breakdown complex
  macromolecules
• amylase made to break down starch to sugar by B.
  subtilis
• Many bacillus species make antibiotics such as
  bacitracin, polymyxin that are released during
  the sporulation process when in the stationary
  phase and after committed to sporulation

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B. thuringienesis

• Produces larvicides that fatal larvae of many
  different groups of insects lepidopterans
  silk worm, cabbage worm, tent caterpillars and
  gypsy moths
• often used as a biological insecticide
• Bacteria makes a toxin that causes intoxication
  by taking the protoxin into the gut and
  converting it to the toxin
• use the gene for the toxin (BT) in plants such as
  corn and cotton to make them resistant to worms
  and larvae

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Clostridium

• Obtain energy only from substrate level
  phosphorylation
• Use anaerobic energy yielding mechanisms
  fermentation
• make butyric acid, or acetone or butanol
• once used commercially to make acetone and
  butanol
• One group ferments cellulose and degrades it in
  the soil

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Butyric Acid and Butanol Formation

• Use glucose to make pyruvate by Embden-Meyer
  pathway
• Pyruvate converted to acetyl CoA, CO2 and H by
  phosphoroclastic rxn
• Acetyl CoA is fermentation product using NADH
  dependent on time for rxn and conditions of
  fermentation make butyric and acetic acid
  initially
• as pH drops, stop making acids and switch to
  butanol and acetone
• keep pH stable with CaCO3 make 3 parts butyric
  acid and 1 part acetic acid (ATP also)

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• Some clostridia ferment AA either individually or
  in pairs where one is the electron donor and the
  other is the electron acceptor
• C. sporegenes catalyzes Ala and Gly by Strickland
  rxn, other pairs also available
• products are always NH3, CO2, carboxylic acid
  with one 1 C than AA oxidized

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Single Fermentation

• Occurs with Ala, Cys, Glu, Gly, His, Ser and Thr
• Acetate, butyrate, CO2 and H2 as end products
• Foul smells related to clostridium growth is
  because of compounds made during growth
• isobutyric acid, isovaleric acid, caproic acid,
  H2S, methylmercaptan (from S-aa), cadaverine
  (lys), putrescine (ornathine) and NH3

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Clostridia

• Most live in the soil in anoxic pockets made
  anoxic by facultative organisms metabolizing
  organic compounds
• Also can live in mammalian intestinal tracts
• Produce a specific toxin or as in gas gangrene, a
  group of toxins
• C. botulinum botulism (food poisoning)
• found in sheep, ducks and variety of other
  animals
• C. tetani tetanus (lock jaw)
• C. perfringens gas gangrene, also causes
  gastroenteritis

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12.21 Cell Wall-less Gram Positive Bacteria
Mycoplasmas

• Lack cell walls
• Smallest organisms capable of autonomous growth
• Simple cell structure and small genomes
• do not stain but similar to gp organisms due to
  low GC content
• Parasitic inhabiting a variety of animal/plant
  hosts
• Resistant to osmotic lysis even though they have
  no cell wall, similar to protoplasts
• presence of sterols in membrane to make it more
  stable

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2 Groups of Mycoplasma

• 1) require sterols in the media
• 2) no requirement for sterols in the medium
• Lipoglycans long chain heteropolysaccharides
  covalently linked to membrane
• similar to LPS but without Lipid A and phosphate
• can also stabilize the membrane and may
  facilitate attachment to receptors on animal cells

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Mycoplasma Morphology

• Small and highly pleomorphic in shape
• probably due to no cell wall
• Smallest free living cells

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12.23 Actinobacteria Mycobacterium

• Rod-shaped bacteria
• Stage of growth staining property that is
  called acid fastness because of a unique lipids
  called mycolic acids only in Mycobacterium
• used in testing TB lesions and for taxonomic
  purposes

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Ziehl-Neelson Stain

• Basic fuchsin and phenol used in stain, slow
  heating drives stains into cells, wash in water,
  decolorize with acid-alcohol and counterstain
  with methylene blue

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Characteristics of Mycobacteria

• Pleomorphic, undergoing branching or filamentous
  growth filaments become fragmented with slight
  disturbances
• 2 Groups slow and fast growers
• M. tuberculosis slow grower, only after days to
  weeks in culture, form tight compact, wrinkled
  colonies probably due to the high lipid
  concentration and hydrophobic nature of cell
  surface

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Growth Requirements

• Relatively simple nutritional requirements
• simple mineral salts medium with NH3 as N source,
  glycerol or acetate as sole C source, electron
  donor is in the air stimulated by lipids and
  fatty acids and egg yolk Lowenstein-Jenson
  medium
• Resist alkali and phenol for a period of time so
  use it to select TB from patients sputum
• treat with 1N NaOH for 30 minutes, neutralize and
  streak to LJ medium

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Pigmentation

• Many mycobacterium can make yellow carotenoid
  pigments
• 3 groups of pigmentation
• non-pigmented M. tuberculosis and M. bovis
• pigmented when grown in light
  photochromogenesis M. kansasii
• may help protect from oxidative damage from light
• pigmented when grown in dark scotochromogenesis
  M. gordonae

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Cord Factor

• M. tuberculosis colony on LJ Medium
• Also makes a long cordlike structures
  aggregation of bacteria cell surface
  glycolipid cord factor

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12.27 The Chlamydia

• Chlamydia and Chlamydophila
• Obligate parasitic bacteria with poor metabolic
  capacities, own phylum
• Have both DNA and RNA
• Cell wall similar to gram negative bacteria
• Simplest biochemical capacities of all known
  bacteria
• Some genes in C. trachoma have eukaryotic look
  may have picked up sequences from host cell

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Human Infections

• Chlamydophila psittaci psittacosis, bird
  infection that can move to humans, pneumonia-like
• Chlamydia trachomatis trachoma and other human
  diseases
• trachoma is an eye disease that causes scarring
  and vascularization of the cornea blindness
• can also cause genitourinary tract infection
  leading cause of sexually transmitted disease -
  1 cause of pelvic inflammatory disease in
  females
• Chlamydophilia pneumoniae respiratory syndromes

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Life Cycle

• 2 cellular types
• elemental body small, dense cell resistant to
  drying and used as a dispersal unit infectious
  form
• reticulate body large, less dense divides by
  binary fission and is the vegetative form,
  non-infectious
• convert to elemental body after several divisions
  so can be released to infect other cells
• Primarily airborne invaders of respiratory tract

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12.33 Spirochetes

• Spirochaeta, Treponema, Leptospira, Borrelia
• Gram negative, motile, tightly coiled bacteria,
  slender and flexuous
• Widespread in aquatic environment and in animals
• Some cause disease including syphilis which is
  sexually transmitted

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Protoplasmic Cylinder

• Structure of spirochetes
• enclosed by cell wall and membrane
• single to many flagella but not similar to other
  bacteria located in periplasm of the cell
  endoflagella
• endoflagella and protoplasmic cylinder are coated
  by outer sheath

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Treponema

• Anaerobic, host-associated spirochetes, commensal
  or parasites of humans or animals
• T. pallidum causative agent of syphilis
• flat wave form see in dark field microscopy to
  ID or look for Ab
• restricted to humans and not grown in culture

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Borrelia

• Majority are animal or human pathogens
• B. recurrentis causative agent of recurring
  fever, insect vector is the human body louse
• high fever and generalized muscular pain 3-7
  days, relapse in 7-9 days, 40 death if not
  treated with tetracycline
• B. burgdorferi causative agent of tickborne
  disease lyme disease
• humans and animals, has linear rather than
  circular DNA